1. Field of the Invention
This invention relates to improvements in mass data storage devices, or the like, and methods for using and operating same, and more particularly to improvements in serial port circuits used in conjunction with mass data storage devices, or the like, and methods for using and operating same.
2. Copyrighted Materials
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
3. Relevant Background
Mass data storage devices include well known hard disk drives that have one or more spinning magnetic disks or platters onto which data is recorded for storage and subsequent retrieval. Hard disk drives may be used in many applications, including personal computers, set-top boxes, video and television applications, audio applications, or some mix thereof. Many applications are still being developed. Applications for hard disk drives are increasing in number, and are expected to further increase in the future.
Typically hard disk drives are sold as an assembly that includes a rotating magnetic medium and a selectively positionable head or data transducer for writing data to and reading data back from the magnetic medium. The assembly also typically includes the necessary electronics to control the rotation of the motor, position of the data transducer or head, conditioning of the data signals associated with the drive, and so on.
In many system architectures and in mass data storage device architectures specifically, Application Specific Integrated Circuits (ASICs) generally communicate to peripheral devices through a serial communication link. This serial communication link is referred to as the "serial port". The serial port is generally used in cases where the data rate requirement is low. The advantage of using the serial port over the use of some sort of parallel interface is the efficient use of package pins for the communication function. A typical serial port requires a three-pin interface, whereas a parallel interface may use as many as 18 pins (for a 16 bit interface). These serial ports are generally bi-directlonal, and typically include three signals: clock, shift-gate, and bidirectional data.
The serial port is usually provided as a part of the read channel electronics that is associated with the hard disk drive. The serial port is generally not used in conjunction with the actual user data processes, but, instead, allows the user access to some of the various registers and other data handling circuitry of the device. Some of the various functions that can be controlled via the serial port, for example, include the gain of the preamplifier associated With the head, the control of the parameters of the head, the speed control for the motor that spins the disk, the control of at least some of the parameters of the voice intro motor (VCM), and so on.
Even though the use of a serial port interface is common in the industry, there is no generally accented standard set that specifies the requirements for timing, logic levels, and so forth. This has resulted in many different and incompatible specifications of serial port interfaces. Each organization that develops an ASIC with a serial port included tends to also generate its own unique interface specification.
Thus, in the past, one of the problems that has been encountered by hard disk drive circuitry manufacturers is the lack of standards defining serial port operations. Therefore, the particular serial port that is associated with any particular drive may differ from those of other drives; that is, each manufacturer may have its own designs and functionalities for its serial ports that are associated with its own drives, and, moreover, may even have different serial port designs among its own different drive models.
As a result of the lack of standards, the serial ports of each disk drive manufacturer are often different from the others. As a result, ASIC designers had to design a unique serial port driver for each application. Sometimes programmability was incorporated into the serial port design with the intent that the serial port would be able to handle several different interface specifications without hardware changes. Repeatedly, however, after the ASIC had been produced, the requirement for a new interface specification would be encountered in the system that would be unique enough that the original serial port driver could not handle it. This, in turn would necessitate the modification of the entire ASIC just to meet the new serial port specification. Consequently, companies that provide ASICs and other supporting chips to the different disk drive manufacturers must custom make each serial port interface to be associated with respective hard drive manufacturer's product. This is time consuming, adds costs to the design of the chip, and adds time that is required for the completion of the chip for delivery.
In many past applications the "non-standard serial port" problem was manageable because the disk drive manufacturer would design an ASIC for a specific disk drive product. The disk drive product was associated with a specific set of peripherals, and the unique serial ports encountered would be designed for as needed. When the next disk drive produce came along (for instance, 10 million units later), an ASIC redesign would be required for the new technology anyway so a new serial port design did not cause any real issue.
A real problem arises, however, when an ASIC manufacturer attempts to design an ASIC product to be sold to many different customers, all of which have different serial port interfaces associated with their products. Since it would not be cost effective to design a specific ASIC for each different customer or for each customer's different application, a need exists for a highly programmable serial port that can handle nearly any specification encountered.
What is needed, therefor, is a circuit and method for enabling the ease of modification of the parameters of a serial port for use in a hard disk drive, or the like.